FLIGHT SERVICE EVALUATION OF COMPOSITE COMPONENTS ON THE BELL MODEL 206L HELICOPTER

The Bell Model 206L LongRanger helicopter was used to gain field experieince with four composite parts in a joint contract sponsored by NASA Langley Research Center and the Structures Laboratory, UASRTL (AVSCOM) under Contract NASI-15279. The four components (vertical fin, forward fairing [engine cowl], litter door, and baggage door) in the evaluation had a 23% weight savings over the production metal parts (total weight saving of 9.2 lb). The parts were flown by various operators throughout North America in four geographical regions: Gulf of Mexico Coastal Region (Texas and Louisiana), Southwest United States (Arizona), Arctic Northwest United States (Alaska), and Northeast United States and Eastern Canada (Quebec, Nova Scotia, and New York City). Almost 500,000 total flight-hours were accumulated by the 160 parts over 12 years of service. The components were removed from service at prescribed intervals and destructively tested to determine strength and stiffness retention as a function of service time and flight-hours. A concurrent testing program was monitored by NASA-Langley, which recorded the residual strength values of test coupons exposed to environmental conditions similar to the parts installed on the forty helicopters. The material systems included in this test program were identical to the systems used to manufactures the flight components. Though the flight components have had very few maintenance problems over the 12 years, the most prominent advantage of the composites was their resistance to corrosion, particularly in the coastal regions. This paper describes the service experieinces and structural test results from the contract.